From 934c2104dc73cac097ded2e95898263739127c02 Mon Sep 17 00:00:00 2001
From: Yacin Tmimi <yacintmimi@gmail.com>
Date: Fri, 30 Sep 2022 12:41:44 -0400
Subject: [PATCH] Handle `dyn*` syntax when rewriting
 `ast::TyKind::TraitObject`

Resolves 5542

Prior to rust-lang/rust#101212 the `ast::TraitObjectSyntax` enum only
had two variants `Dyn` and `None`. The PR that introduced the `dyn*`
syntax added a new variant `DynStar`, but did not update the formatting
rules to account for the new variant.

Now the new `DynStar` variant is properly handled and is no longer
removed by rustfmt.
---
 src/types.rs               | 16 +++++++++-------
 tests/target/issue_5542.rs | 10 ++++++++++
 2 files changed, 19 insertions(+), 7 deletions(-)
 create mode 100644 tests/target/issue_5542.rs

diff --git a/src/types.rs b/src/types.rs
index 25ad587ba85..f487fbc0f5d 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -664,9 +664,11 @@ impl Rewrite for ast::Ty {
         match self.kind {
             ast::TyKind::TraitObject(ref bounds, tobj_syntax) => {
                 // we have to consider 'dyn' keyword is used or not!!!
-                let is_dyn = tobj_syntax == ast::TraitObjectSyntax::Dyn;
-                // 4 is length of 'dyn '
-                let shape = if is_dyn { shape.offset_left(4)? } else { shape };
+                let shape = match tobj_syntax {
+                    ast::TraitObjectSyntax::Dyn => shape.offset_left(4)?, // 4 is offset 'dyn '
+                    ast::TraitObjectSyntax::DynStar => shape.offset_left(5)?, // 5 is offset 'dyn* '
+                    ast::TraitObjectSyntax::None => shape,
+                };
                 let mut res = bounds.rewrite(context, shape)?;
                 // We may have falsely removed a trailing `+` inside macro call.
                 if context.inside_macro() && bounds.len() == 1 {
@@ -674,10 +676,10 @@ impl Rewrite for ast::Ty {
                         res.push('+');
                     }
                 }
-                if is_dyn {
-                    Some(format!("dyn {}", res))
-                } else {
-                    Some(res)
+                match tobj_syntax {
+                    ast::TraitObjectSyntax::Dyn => Some(format!("dyn {}", res)),
+                    ast::TraitObjectSyntax::DynStar => Some(format!("dyn* {}", res)),
+                    ast::TraitObjectSyntax::None => Some(res),
                 }
             }
             ast::TyKind::Ptr(ref mt) => {
diff --git a/tests/target/issue_5542.rs b/tests/target/issue_5542.rs
new file mode 100644
index 00000000000..730bb7b681a
--- /dev/null
+++ b/tests/target/issue_5542.rs
@@ -0,0 +1,10 @@
+#![feature(dyn_star)]
+#![allow(incomplete_features)]
+
+use core::fmt::Debug;
+
+fn main() {
+    let i = 42;
+    let dyn_i = i as dyn* Debug;
+    dbg!(dyn_i);
+}